Clock Synchronization
Every device in a capture setup keeps its own clock, and no two agree exactly. Clock synchronization is how the software works out the relationship between them. It is what lets a force reading and a video frame from the same instant line up as the same instant.
Version 26.1 improved how the software does this.
What poor timing costs you
A swing lasts about a second, and the parts of it you coach from are much shorter. Weight moving from the back foot to the front foot, the club reaching the top, impact: these are separated by tens of milliseconds.
If the cameras and the plates disagree about what time it is, every measurement that combines them is wrong by that amount. The picture is fine and the force trace is fine, but the force number you read off at impact belongs to a slightly different instant than the frame you are looking at.
That error does not announce itself. Nothing looks broken. The numbers are simply attached to the wrong moment, and the further out the clocks are, the more misleading they get.
How much error is acceptable depends on what you are combining. Reading ground force against video is the demanding case, because the two are read together at a single instant. For a camera that reports its timing quality, the software judges this for you and warns when it is not good enough. Not every camera reports it. A camera that does not gets no warning either way, so silence is not proof that timing is good.
What it does not affect
Clock synchronization is about combining two or more sources. It does not affect:
- A single camera on its own. The frames within one recording are timed by that camera.
- The force trace on its own.
- Anything about video quality, resolution or frame rate.
So a sync problem shows up in comparisons, not in any one source.
The accuracy warning
The software can tell you that timing accuracy is worse than it wants. The message looks like this:
Clock sync accuracy is ±0.00ms, above the target for reliable multi-camera timing.
The zeros are a placeholder. On screen you see the measured figure in their place.
It means the software measured the agreement between clocks, found it worse than the target, and is telling you before you record rather than after.
The reading is a measurement, not a fault code. It can improve on its own once everything is connected and running, because working out the offset between two clocks takes repeated observations.
What to do about it
In order, stopping when it clears:
- Wait with everything connected. Synchronization settles over repeated measurements. A warning can appear right after you plug something in and clear on its own.
- Check the network path for phone cameras. A phone syncs over WiFi. A busy or weak network makes the figure worse. Move the phone closer to the access point, or put it on a less crowded network.
- Reconnect the device the warning names. Unplug and replug a USB camera, or disconnect and reconnect a phone.
- Reduce what shares the connection. Several cameras on one USB controller, or a network carrying a video stream and the sync traffic together, both make it worse.
- Restart the software with everything already connected, so it starts synchronization from a clean state.
If the figure stays bad after all of that, report it. Say which devices are connected, how they are connected, and what number the warning shows.
What affects it in a setup
- How devices connect. A wired connection is steadier than WiFi, for phones as well as cameras. A device on its own USB controller is steadier than one sharing it.
- Network quality, for anything that syncs over the network. Interference, distance and other traffic all cost accuracy.
- How long things have been running. A setup that has been running for a while has more measurements behind it than one just switched on.
- Sleep and power saving. A laptop that suspends a USB port or throttles the network interrupts synchronization and it has to recover.
Related: Using a phone as a camera , where the warning most often appears.
Related
- Using a phone as a camera , where the accuracy warning appears most often
- What’s new in 26.1